South Columbia

A Special Public Avalanche Warning is in effect. Copy this link to view details: http://bit.ly/2nSOUyX

High -

An Arctic air mass keeps things cold and dry until Tuesday, when light snow is expected, with milder temperatures and strong south-westerly winds.More details can be found in the Mountain Weather Forecast.

A very large, widespread avalanche cycle was observed on Thursday, with a few events continuing on Friday. Slopes of all aspects and elevations ran full path and reached valley floor. In some cases, mature timber was smashed. These failed on all of the persistent weak layers discussed in the snowpack section. Avalanches involving only the recent storm snow were also very large.The natural cycle is winding down, but human-triggering remains a real concern. You might be surprised by how large an avalanche can be triggered and how far it could run.

Large cornices are looming. Moderate north to north-westerly winds have shifted 30-40 cm recent storm snow into wind slabs on lee slopes. This adds to an existing storm slab 1-2.5 m deep from the last couple of weeks accumulation. Some solar effect was observed on Friday and sun crusts or moist snow may be found, depending on the time of day.Several persistent weak layers make up a troublesome snowpack which is not tolerating the recent load. In the top 1.5-2.5 m of the snowpack, two surface hoar/ crust layers buried in January can be found. Expect to find one or other of these on all aspects and elevations.Deeper in the snowpack (around 200 cm deep) is a facet/crust/surface hoar layer from December, most prevalent at and below treeline.Near the base of the snowpack is a crust/facet combo, most likely to be triggered from thin spots in the alpine.All of these layers have produced large avalanches recently. The wide distribution and ongoing reactivity of these layers suggests that avoidance through choosing simple terrain is the best strategy.